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==Multi-conformer model of Ketosteroid Isomerase from Pseudomonas Putida (pKSI) bound to 4-Androstenedione at 250 K==
<StructureSection load='6ucy' size='340' side='right'caption='[[6ucy]], [[Resolution|resolution]] 1.15&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6ucy]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Pseudomonas_putida Pseudomonas putida]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6UCY OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6UCY FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.15&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ASD:4-ANDROSTENE-3-17-DIONE'>ASD</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=6ucy FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6ucy OCA], [https://pdbe.org/6ucy PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6ucy RCSB], [https://www.ebi.ac.uk/pdbsum/6ucy PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6ucy ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SDIS_PSEPU SDIS_PSEPU] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
How enzymes achieve their enormous rate enhancements remains a central question in biology, and our understanding to date has impacted drug development, influenced enzyme design, and deepened our appreciation of evolutionary processes. While enzymes position catalytic and reactant groups in active sites, physics requires that atoms undergo constant motion. Numerous proposals have invoked positioning or motions as central for enzyme function, but a scarcity of experimental data has limited our understanding of positioning and motion, their relative importance, and their changes through the enzyme's reaction cycle. To examine positioning and motions and test catalytic proposals, we collected "room temperature" X-ray crystallography data for Pseudomonas putida ketosteroid isomerase (KSI), and we obtained conformational ensembles for this and a homologous KSI from multiple PDB crystal structures. Ensemble analyses indicated limited change through KSI's reaction cycle. Active site positioning was on the 1- to 1.5-A scale, and was not exceptional compared to noncatalytic groups. The KSI ensembles provided evidence against catalytic proposals invoking oxyanion hole geometric discrimination between the ground state and transition state or highly precise general base positioning. Instead, increasing or decreasing positioning of KSI's general base reduced catalysis, suggesting optimized Angstrom-scale conformational heterogeneity that allows KSI to efficiently catalyze multiple reaction steps. Ensemble analyses of surrounding groups for WT and mutant KSIs provided insights into the forces and interactions that allow and limit active-site motions. Most generally, this ensemble perspective extends traditional structure-function relationships, providing the basis for a new era of "ensemble-function" interrogation of enzymes.

Assessment of enzyme active site positioning and tests of catalytic mechanisms through X-ray-derived conformational ensembles.,Yabukarski F, Biel JT, Pinney MM, Doukov T, Powers AS, Fraser JS, Herschlag D Proc Natl Acad Sci U S A. 2020 Dec 29;117(52):33204-33215. doi:, 10.1073/pnas.2011350117. Epub 2020 Dec 21. PMID:33376217<ref>PMID:33376217</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6ucy" style="background-color:#fffaf0;"></div>

==See Also==
*[[Ketosteroid Isomerase|Ketosteroid Isomerase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Pseudomonas putida]]
[[Category: Biel JT]]
[[Category: Fraser JS]]
[[Category: Herschlag D]]
[[Category: Yabukarski F]]